A liquid composition being a constituent of a cosmetic product such as a fragrance product like perfume or cologne, such as an enamel remover, should be colored appropriately for promoting its attractive appearance. For example, a fragrance product has been colored so far with a colorant such as a pigment or dye, since it should be characterized not only by its aroma, effectiveness and usability but also by its appearance for the purpose of emphasizing its uniqueness. In response to a further diversity of the consumer's demand, in addition to just coloring itself, a fragrance product whose appearance was further characterized was developed. Thus, it was a 2-phase type fragrance product wherein there were two liquid phases separated from each other and colored with colorants such as die and pigment to have different color, and when the phases were mixed and dispersed, the product could exhibit the mixed color.
Otherwise, such a color development can also be accomplished by utilizing the difference in the refractive index between the two phases. Thus, Francis et al reported the phenomenon called “chromatic emulsion” in J. Phys. Chem. in 1952. In this phenomenon, an aurora-like beautiful color is developed when the difference is small in the refractive index between an oil phase and an aqueous phase in a surfactant-supplemented liquid-liquid emulsified dispersion.
Nevertheless, when a color is imparted using a pigment as a colorant, it is difficult to provide a transparent pigment-containing dispersion because of too large difference in the refractive index between the pigment and the dispersion medium which leads to a turbidness, although the color is intense and the color tone is bright. The specific gravity of a pigment which is often high may also allow the sedimentation to occur readily, resulting in a difficulty in re-dispersing.
On the other hand, when a dye is employed as a colorant for imparting a color, its solution poses a problem due to the adhesion to a skin or clothes and it is difficult to be washed off once adhered, although it allows the color adjustment to be accomplished easily. In addition, some dyes involved are problematically hazardous to human health, and are subjected to the limitation of use. Moreover, the weatherability of a pigment or dye, especially of an organic dye, is problematic, and the discoloration under a light such as sunlight or fluorescent lamp leads to a poor stability during storage.
The 2-phase fragrance product described above, which employs a colorant, also posed the problems due to the colorant, such as a discoloration depending on the stability of the colorant. While a 2-phase fragrance product can be imparted with a further aspect if it develops a color upon mixing though it is a colorless before mixing, such an aspect is difficult to be imparted when using a colorant.
In the method for developing a color utilizing the difference in the refractive index between two phases, since the dispersion system employed is a liquid-liquid system in which particles were formed by emulsifying the system in the presence of a surfactant, the system undergoes a sustained deterioration of the emulsion system due to aggregation, coalescence or the like, resulting in a problem in applications where the color development should be maintained stably.